The present invention is directed to methods and devices for filtering fluid flow through body structures. Such devices are used in various parts of the body, such as the vascular system, to filter out unwanted material.
Filters are used in the vascular system to remove plaque and other material which can obstruct blood vessels. Vascular filtering devices may be used during other procedures such angioplasty, stenting, endarterectomy or atherectomy. During such interventional procedures, there is a danger of breaking plaque free from the vessel walls. Filters are used to prevent plaque and other material which may be dislodged during such interventional procedures from traveling downstream where they can obstruct or restrict blood flow.
A filtering device is disclosed in WO 98/33443 which published Aug. 6, 1998 by inventor Jay Yadav which is hereby incorporated by reference. One of the filters disclosed in the published application at FIG. 9 shows a filter which is expanded with a single spiral structural wire attached to the filter. A fiber is attached to the spiral wire and tension is applied by the fiber to collapse the spiral wire. When tension on the fiber is released, the wire and attached filter expand.
The present invention is directed to improved methods and devices for filtering fluid flow in patients and, in particular, for filtering blood flow.
The filter device of the present invention has a filter element and an expandable element which expands the filter element. The filter element is preferably biased toward the collapsed position and the expandable element is preferably biased toward the expanded position. The expandable element is tensioned to hold the expandable element in the collapsed shape. Tension is released to permit the expandable element to expand the filter element. The proximal end of the filter element is preferably biased toward the collapsed position so that material trapped in the filter element cannot escape when the filter device is collapsed and removed.
The expandable element preferably slides against an interior surface of the filter element to expand the filter element. The sliding engagement between the filter element and expandable element permits the filter element to expand to various intermediate sizes for filtering varying size vessels. The sliding engagement between the filter element and the expandable element also permits the filter element and the expandable element to lengthen, distort, and rotate independently of one another which cannot occur with the filter device of WO 98/33443 described above.
The expandable element is preferably formed with less than three filaments and preferably only one filament. The filament advantageously can be collapsed to a diameter of less than 0.040 inch so that the filter device can access small, tortuous vessels. The filament preferably forms a coil in the expanded position which has an increasing diameter proximally to form a conical shape.
The filter element may be any suitable material such as an elastomeric membrane or a mesh structure. The filter element is attached to a core element and is collapsed around the core element and expandable element. The expandable element is preferably slidably coupled to the core element with a loop, interlocking connection or coaxial configuration.
These and other features and advantages of the invention will become apparent from the following description of the preferred embodiments, drawings and claims.